1. Field of the Invention
This invention relates to a method of manufacture of semiconductor memory devices and more particularly manufacture of electrical connection to bit lines in memory devices and the devices manufacturee thereby.
2. Description of Related Art
U.S. Pat. No. 5,204,286 of Doan for "Method of Making Self-Aligned Contacts and Vertical Interconnects to Integrated Circuits" and U.S. Pat. No. 5,231,051 of Baldi et al for "Method for Formation of Contact Plugs Utilizing Etchback" show use of deposits of tungsten which are etched back to form contacts.
In a conventional EPROM (Flash memory) layout, the source line is a diffusion type which must connect to a metal pick-up for about 16 cells. In addition, the drain contact to the poly is not self-aligned. Both of these factors limit the ability to reduce the scale (dimensions) of EPROM (Flash) memory devices.